Jaguar V12 Engine - 5.3-litre HE

5.3-litre HE

A high-efficiency 5.3 HE version debuted in 1981. This used the special high-swirl design "May" cylinder heads, and had an unusually high compression ratio (10.5:1 – 12.5:1, depending on market and year). In any given market, power levels remained similar to the previous model, but fuel economy was improved by nearly 50%. The HE V12 engines had a fuel injection system from Lucas (dubbed Lucas Digital P) which was based on the Bosch D-Jetronic system.

The Lucas CEI ignition system continued until mid-1989, when it was superseded on the XJ-S by a system from Magneti Marelli. Series 3 XJ12 and Daimler Double Six cars used the Lucas CEI system until the end of production in 1992. The Marelli ignition system was used until the end of XJ-S production and on the 6.0 L V12 used in the XJ81 four-door saloons made in 1993 and 1994.

The 5.3 HE was used in these cars:

• 1981-1992 Jaguar XJ12 (Series 3)
• 1981-1992 Jaguar XJS
• 1981-1992 Daimler Double-Six (Series 3)